$ git clone -n https://src.fedoraproject.org/rpms/rust-nu-system.git /var/lib/mock/f40-build-2712755-72063/root/chroot_tmpdir/scmroot/rust-nu-system
Cloning into '/var/lib/mock/f40-build-2712755-72063/root/chroot_tmpdir/scmroot/rust-nu-system'...
$ git fetch origin 7da7f251f49f6b75c09e2147e61405e7357a5812:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-nu-system
 * [new ref]         7da7f251f49f6b75c09e2147e61405e7357a5812 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7da7f25 Update to 0.91.0 (rhbz#2257513)